Fixed volume valve system

ABSTRACT

Embodiments of the present invention provide valves that provide for uniform holdup volume. An embodiment of the present invention provides a valve comprising a valve body (e.g., one or more pieces) that defines a valve chamber having a valve seat, an inlet flow passage, an outlet flow passage and a diaphragm control flow passage intersecting the valve seat. The valve seat is shaped so that the valve has a fixed holdup volume when at least a threshold vacuum is applied to the diaphragm control flow passage. The valve further comprises a diaphragm movable towards and away from the valve seat. According to one embodiment of the present invention, the valve seat can have a semi-hemispherical shape to which the diaphragm conforms when a minimum vacuum is applied to the diaphragm control flow passage.

RELATED APPLICATIONS

The present application claims under 35 U.S.C. 119(e) priority to and the benefit of U.S. Provisional Application No. 60/742,147, entitled “VALVE PLATE SYSTEM AND METHOD” by Iraj Gashgaee et al., filed Dec. 2, 2005, [Atty. Dkt. No. ENTG1770] which is hereby fully incorporated by reference herein.

TECHNICAL FIELD OF THE INVENTION

This invention relates generally fluid valves. More particularly, embodiments of the present invention relate to valves for multi-stage pumps. Even more particularly, embodiments of the present invention relate to a valve plate that reduces hold up volume.

BACKGROUND OF THE INVENTION

There are many applications for which precise control over the amount and/or rate at which a fluid is dispensed by a pumping apparatus is necessary. In semiconductor processing, for example, it is important to control the amount and rate at which photochemicals, such as photoresist chemicals, are applied to a semiconductor wafer. The coatings applied to semiconductor wafers during processing typically require a flatness across the surface of the wafer that is measured in angstroms. The rate at which processing chemicals are applied to the wafer has to be controlled in order to ensure that the processing liquid is applied uniformly.

The repeatability of a dispense operation is effected, in part, by precisely controlling the amount of fluid in various portions of the multi-stage pumps at different stages in the dispense cycle. Some valve designs, however, exhibit characteristics that reduce repeatability. In many multi-stage pumps, the hold up volume of a valve (i.e., the volume of fluid in the valve when the valve is open) depends largely on the pressure/vacuum used to open the valve. As the pressure/vacuum increases, the amount of hold up volume also increases. When the valve closes, the hold up volume of fluid is forced elsewhere in the pump, such as to a pump chamber. Thus, the amount of fluid entering another portion of the pump due to a valve closing varies depending on the amount of pressure/vacuum applied to open the valve.

The house pressure/vacuum used to open the valves is often not well controlled relative to the precision required in semiconductor manufacturing. Hence, during each dispense operation, a different amount of fluid may be in the dispense chamber due to the variable hold up volumes of pump valves. The repeatability of the dispense operation is consequently reduced.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide valve systems and methods that substantially eliminate or reduce the disadvantages of previously developed valve systems and methods. More particularly, one embodiment of the present invention provides a valve comprising a valve body (e.g., one or more pieces) that defines a valve chamber having a valve seat, an inlet flow passage, an outlet flow passage and a diaphragm control flow passage intersecting the valve seat. The valve seat is shaped so that the valve has a fixed holdup volume when at least a threshold vacuum is applied to the diaphragm control flow passage. The valve further comprises a diaphragm movable towards and away from the valve seat. According to one embodiment of the present invention, the valve seat can have a semi-hemispherical shape to which the diaphragm conforms when a minimum vacuum is applied to the diaphragm control flow passage. It should be noted that the “semi-hemispherical” shape, for purposes of this application, can include a full hemisphere.

Another embodiment of the present invention comprises a valve assembly having a valve (e.g., a purge valve or other valve). The valve assembly comprises a first piece, such as a pump body, and a second piece, such as a valve plate, coupled together. The valve body defines a valve chamber. The first piece of the valve body defines a first flow passage (e.g., an inlet flow passage) and a second flow passage (e.g., an outlet flow passage) intersecting the valve chamber and the second piece defines a valve seat and a third flow passage (e.g., a diaphragm control flow passage) intersecting the first valve seat. The valve assembly further comprises a valve diaphragm movable within the valve chamber. The valve seat is shaped so that the valve diaphragm conforms to the valve seat to provide a fixed valve holdup volume when a threshold or greater vacuum is applied to the third flow passage.

Yet another embodiment of the present invention comprises a multistage pump having a feed chamber and a dispense chamber. The multistage pump comprises a pump body and a valve plate. The pump body defines an inlet flow passage to and an outlet flow passage from a first valve and the valve plate defines a valve seat for the first valve. The multi-stage pump further comprises a valve diaphragm movable in the first valve. According to one embodiment the first valve seat is shaped so that the first valve diaphragm conforms to the first valve seat to provide a fixed holdup volume when a threshold or greater vacuum is applied to the first valve. The valve plate and pump body can also define other valves used to regulate flow in the multistage pump.

Embodiments of the present invention provide an advantage by eliminating or reducing the variability of hold up volume caused by outside influences. For example, embodiments of the present invention provide an advantage by reducing the effects of vacuum pressure on the displacement volume of a valve.

Embodiments of the present invention provide yet another advantage by reducing the hold up volume of a valve.

Embodiments of the present invention provide yet another advantage by increasing diaphragm life through reduced stress on the diaphragm.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and the advantages thereof may be acquired by referring to the following description, taken in conjunction with the accompanying drawings in which like reference numbers indicate like features and wherein:

FIG. 1 is a diagrammatic representation of a multiple stage pump (“multi-stage pump”) according to one embodiment of the present invention;

FIGS. 2 and 3 are diagrammatic representations of one embodiment of a multi-stage pump;

FIG. 4 is a diagrammatic representation illustrating the construction of one or more valves according to one embodiment of a valve plate and dispense block;

FIG. 5A is a diagrammatic representation of a side view of a dispense block and FIG. 5B is a diagrammatic representation of an end surface of the dispense block;

FIG. 6 is a diagrammatic representation of one embodiment of a valve plate;

FIG. 7 is a diagrammatic representation of another view of an embodiment of a valve plate;

FIG. 8 is a diagrammatic representation of a view of an embodiment of a valve plate showing passages defined in the valve plate;

FIG. 9A is a diagrammatic representation of a valve plate having a flat valve chamber;

FIG. 9B is a diagrammatic representation of a valve plate having a semi-hemispherical valve chamber;

FIG. 10 is a graph illustrating the reduction in displacement volume fluctuations due to vacuum for a semi-hemispherically shaped valve chamber;

FIG. 11A is a diagrammatic representation of one embodiment of a portion of a valve plate;

FIG. 11B is a diagrammatic representation of another embodiment of a portion of a valve plate;

FIG. 12 is a diagrammatic representation of one embodiment of a diaphragm; and

FIG. 13 is a diagrammatic representation of a single stage pump.

DETAILED DESCRIPTION

Preferred embodiments of the present invention are illustrated in the FIGUREs, like numerals being used to refer to like and corresponding parts of the various drawings. To the extent dimensions are provided, they are provided by way of example for particular implementations and are not provided by way of limitation. Embodiments can be implemented in a variety of configurations.

Broadly speaking, embodiments of the present invention provide valves that are configured to have a fixed hold up volume once a threshold condition is met. For example, the valves can be configured to have a fixed holdup volume once a threshold pressure/vacuum is applied to open the valve.

According to one embodiment a valve can comprise a valve body defining a valve chamber having a valve seat, an inlet flow passage, an outlet flow passage and a diaphragm control flow passage. The valve body, according to one embodiment, can be made of multiple pieces such as a pump body and a valve plate. A diaphragm is movable towards and away from the valve seat based on the application of pressure/vacuum to the diaphragm control flow passage. The valve seat is shaped so that the valve has a fixed holdup volume when at least a threshold vacuum is applied to the diaphragm control flow passage. For example, the valve seat can have a semi-hemispherical shape to which the diaphragm conforms when the valve is open.

According to various embodiments, various valves with fixed holdup volumes can be at least partially integrated into a valve plate of a multi-stage pump used for dispensing chemicals to a wafer. The valve plate and pump body can sandwich a diaphragm that acts as the diaphragm for one or more of the valves of the multi-stage pump. FIGS. 2-3 below describe one embodiment of a multi-stage pump and FIGS. 4-9, 11A and 11B describe various components of one embodiment of a valve system for the multi-stage pump.

FIG. 1 is a diagrammatic representation of a multi-stage pump 100. Multi-stage pump 100 includes a feed stage portion 105 and a separate dispense stage portion 110. Located between feed stage portion 105 and dispense stage portion 110, from a fluid flow perspective, is filter 120 to filter impurities from the process fluid. A number of valves can control fluid flow through multi-stage pump 100 including, for example, inlet valve 125, isolation valve 130, barrier valve 135, purge valve 140, vent valve 145 and outlet valve 147. Dispense stage portion 110 can further include a pressure sensor 112 that determines the pressure of fluid at dispense stage 110. The pressure determined by pressure sensor 112 can be used to control the speed of the various pumps as described below. Example pressure sensors include ceramic and polymer pesioresistive and capacitive pressure sensors, including those manufactured by Metallux AG, of Korb, Germany. According to one embodiment, the face of pressure sensor 112 that contacts the process fluid is a perfluoropolymer. Pump 100 can include additional pressure sensors, such as a pressure sensor to read pressure in feed chamber 155.

Feed stage 105 and dispense stage 110 can include rolling diaphragm pumps to pump fluid in multi-stage pump 100. Feed-stage pump 150 (“feed pump 150”), for example, includes a feed chamber 155 to collect fluid, a feed stage diaphragm 160 to move within feed chamber 155 and displace fluid, a piston 165 to move feed stage diaphragm 160, a lead screw 170 and a stepper motor 175. Lead screw 170 couples to stepper motor 175 through a nut, gear or other mechanism for imparting energy from the motor to lead screw 170. According to one embodiment, feed motor 170 rotates a nut that, in turn, actuates lead screw 170, causing piston 165 to actuate. Dispense-stage pump 180 (“dispense pump 180”) can similarly include a dispense chamber 185, a dispense stage diaphragm 190, a piston 192, a lead screw 195, and a dispense motor 200. According to other embodiments, feed stage 105 and dispense stage 110 can each be include a variety of other pumps including pneumatically actuated pumps, hydraulic pumps or other pumps. One example of a multi-stage pump using a pneumatically actuated pump for the feed stage and a stepper motor driven hydraulic pump is described in U.S. patent application Ser. No. 11/051,576, entitled “PUMP CONTROLLER FOR PRECISION PUMPING APPARATUS” by Inventors Zagars, et al., filed Feb. 4, 2005, [Atty. Dkt. No. ENTG1420-2], which is hereby fully incorporated by reference herein.

Feed motor 175 and dispense motor 200 can be any suitable motor. According to one embodiment, dispense motor 200 is a Permanent-Magnet Synchronous Motor (“PMSM”). The PMSM can be controlled by a digital signal processor (“DSP”) utilizing Field-Oriented Control (“FOC”) or other position/speed control scheme at motor 200, a controller onboard multi-stage pump 100 or a separate pump controller. PMSM 200 can further include an encoder (e.g., a fine line rotary position encoder) for real time feedback of dispense motor 200's position. The use of a position sensor gives accurate and repeatable control of the position of piston 192, which leads to accurate and repeatable control over fluid movements in dispense chamber 185. For, example, using a 2000 line encoder, which according to one embodiment gives 8000 pulses to the DSP, it is possible to accurately measure to and control at 0.045 degrees of rotation. In addition, a PMSM can run at low velocities with little or no vibration. Feed motor 175 can also be a PMSM or a stepper motor. U.S. Provisional Patent Application No. 60/741,660 entitled “SYSTEM AND METHOD FOR POSITION CONTROL OF A MECHANICAL PISTON IN A PUMP” by Gonnella et al., filed Dec. 2, 2005, [Atty. Dkt. No. ENTG1750], U.S. Provisional Patent Application No. 60/841,725, entitled “SYSTEM AND METHOD FOR POSITION CONTROL OF A MECHANICAL PISTON IN A PUMP”, by Gonnella et al., filed Sep. 1, 2006 [Atty. Dkt. No. ENTG1750-1] and U.S. patent application Ser. No. ______, entitled “SYSTEM AND METHOD FOR POSITION CONTROL OF A MECHANICAL PISTON IN A PUMP”, by Inventors Gonnella et al., filed _(——————), [Atty. Dkt. No. ENTG1750-2], which are hereby incorporated by reference herein, describe embodiments of a pump utilizing a PMSM, which is hereby fully incorporated by reference herein. According to one embodiment, feed motor 175 can be an EAD Motors of Dover, N.H. stepper motor part no. L1 LAB-005 and dispense motor 200 can be an EAD Motors brushless DC Motor part no. DA23 DBBL-13E17A.

The valves of multi-stage pump 100 are opened or closed to allow or restrict fluid flow to various portions of multi-stage pump 100. According to one embodiment, these valves can be pneumatically actuated (i.e., gas driven) diaphragm valves that open or close depending on whether pressure or a vacuum is asserted. One embodiment of a valve plate for housing diaphragm valves is described below in conjunction with FIGS. 6-9B.

FIG. 2 is a diagrammatic representation of one embodiment of a pump assembly for multi-stage pump 100. Multi-stage pump 100 can include a dispense block 205 that defines various fluid flow paths through multi-stage pump 100. Dispense pump block 205, according to one embodiment, can be a unitary block of PTFE, modified PTFE or other material. Because these materials do not react with or are minimally reactive with many process fluids, the use of these materials allows flow passages and pump chambers to be machined directly into dispense block 205 with a minimum of additional hardware. Dispense block 205 consequently reduces the need for piping by providing a fluid manifold.

Dispense block 205 can include various external inlets and outlets including, for example, inlet 210 through which the fluid is received, vent outlet 215 for venting fluid during the vent segment, and dispense outlet 220 through which fluid is dispensed during the dispense segment. Dispense block 205, in the example of FIG. 2, does not include an external purge outlet as purged fluid is routed back to the feed chamber. In other embodiments of the present invention, however, fluid can be purged externally.

Dispense block 205 routes fluid to the feed pump, dispense pump and filter 120. A pump cover 225 can protect feed motor 175 and dispense motor 200 from damage, while piston housing 227 can provide protection for piston 165 and piston 192. Valve plate 230 provides a valve housing for a system of valves (e.g., inlet valve 125, isolation valve 130, barrier valve 135, purge valve 140 and vent valve 145 of FIG. 1) that can be configured to direct fluid flow to various components of multi-stage pump 100. According to one embodiment, each of inlet valve 125, isolation valve 130, barrier valve 135, purge valve 140, and vent valve 145 is partially integrated into valve plate 230 and is a diaphragm valve that is either opened or closed depending on whether pressure or vacuum is applied to the corresponding diaphragm.

Valve plate 230 includes a valve control inlet for each valve to apply pressure or vacuum to the corresponding diaphragm. For example, inlet 235 corresponds to barrier valve 135, inlet 240 to purge valve 140, inlet 245 to isolation valve 130, inlet 250 to vent valve 145, and inlet 255 to inlet valve 125. By the selective application of pressure or vacuum to the inlets, the corresponding valves are opened and closed. The valves can be opened and closed in various sequences such as described in United States patent Application Nos. U.S. Provisional Patent Application No. 60/742,168, entitled “SYSTEM AND METHOD FOR VALVE SEQUENCING IN A PUMP”, by inventors Gonnella et al., filed Dec. 2, 2005, [Atty. Dkt. No. ENTG1740] and U.S. patent application Ser. No. ______, entitled “SYSTEM AND METHOD FOR VALVE SEQUENCING IN A PUMP”, by Inventors Gonnella et al., filed _(——————), [Atty. Dkt. No. ENTG1740-1], which are hereby fully incorporated by reference herein. Valve plate 230 can be configured to reduce the hold-up volume of the valves, eliminate volume variations due to vacuum fluctuations, reduce vacuum requirements and reduce stress on the valve diaphragm.

A valve control gas and vacuum are provided to valve plate 230 via valve control supply lines 260, which run from a valve control manifold (covered by manifold cover 263 or housing cover 225), through dispense block 205 to valve plate 230. Valve control gas supply inlet 265 provides a pressurized gas to the valve control manifold and vacuum inlet 270 provides vacuum (or low pressure) to the valve control manifold. The valve control manifold acts as a three way valve to route pressurized gas or vacuum to the appropriate inlets of valve plate 230 via supply lines 260 to actuate the corresponding valve(s).

FIG. 3 is a diagrammatic representation of one embodiment of multi-stage pump 100 with dispense block 205 made transparent to show the fluid flow passages defined there through. Dispense block 205 defines various chambers and fluid flow passages for multi-stage pump 100. According to one embodiment, feed chamber 155 and dispense chamber 185 can be machined directly into dispense block 205. Additionally, various flow passages can be machined into dispense block 205. A fluid flow passage runs from inlet 210 to the inlet valve. Fluid flow passage 280 runs from the inlet valve to feed chamber 155, to complete the path from inlet 210 to feed pump 150. Inlet valve 125 in valve housing 230 regulates flow between inlet 210 and feed pump 150. Flow passage 285 routes fluid from feed pump 150 to isolation valve 130 in valve plate 230. The output of isolation valve 130 is routed to filter 120 by another flow passage. Fluid flows from filter 120 through flow passages that connect filter 120 to the vent valve 145 and barrier valve 135. The output of vent valve 145 is routed to vent outlet 215 while the output of barrier valve 135 is routed to dispense pump 180 via flow passage 290. Dispense pump, during the dispense segment, can output fluid to outlet 220 via flow passage 295 or, in the purge segment, to the purge valve through flow passage 300. During the purge segment, fluid can be returned to feed pump 150 through flow passage 305. Because the fluid flow passages can be formed directly in the PTFE (or other material) block, dispense block 205 can act as the piping for the process fluid between various components of multi-stage pump 100, obviating or reducing the need for additional tubing. In other cases, tubing can be inserted into dispense block 205 to define the fluid flow passages.

FIG. 3 further shows supply lines 260 for providing pressure or vacuum to valve plate 230. Actuation of the valves is controlled by the valve control manifold 302 that directs either pressure or vacuum to each supply line 260. Each supply line 260 can include a fitting (an example fitting is indicated at 318) with a small orifice (i.e., a restriction). The orifice in each supply line helps mitigate the effects of sharp pressure differences between the application of pressure and vacuum to the supply line. This allows the valves to open and close more smoothly and more slowly.

According to one embodiment, dispense pump and/or feed pump 150 can be a rolling diaphragm pump as described in U.S. Provisional Patent Application No. 60/742,435, entitled “SYSTEM AND METHOD FOR MULTI-STAGE PUMP WITH REDUCED FORM FACTOR” by Gonnella et al, filed Dec. 5, 2005, [Atty. Dkt. No. ENTG1720], and U.S. patent application Ser. No. ______, entitled “SYSTEM AND METHOD FOR A PUMP WITH REDUCED FORM FACTOR”, by inventors Cedrone et al., filed _(——————), [Atty. Dkt. No. ENTG1720-1] which are hereby fully incorporated by reference herein. It should be noted that the multi-stage pump 100 described in conjunction with FIGS. 1-3 is provided by way of example, but not limitation, and embodiments of the present invention can be implemented for other multi-stage pump configurations.

FIG. 4 illustrates one embodiment of various components used in forming input valve 125, isolation valve 130, barrier valve 135, purge valve 140 and vent valve 145 according to one embodiment of the present invention. Output valve 147 is external to the pump in this embodiment. As shown in FIG. 4, dispense block 205 has an end surface 1000 upon which diaphragm 1002 is placed. O-rings 1004 are aligned with corresponding rings on end surface 1000 and press diaphragm 1002 partially into the rings in dispense block 205. Valve plate 230 also includes corresponding rings in which O-rings 1004 are at least partially seated. Valve plate 230 is connected to dispense block 205 using washers and screws (shown at 1006 and 1008). Thus, as shown in FIG. 4, the body of each valve can be formed of multiple pieces such as the dispense block (or other part of the pump body) and a valve plate. A sheet of elastomeric material, illustrated as diaphragm 1002, is sandwiched between valve plate 230 and dispense block 205 to form the diaphragms of the various valves. Diaphragm 1002, according to one embodiment of the present invention can be a single diaphragm used for each of input valve 125, isolation valve 130, barrier valve 135, purge valve 140 and vent valve 145. Diaphragm 1002 can be PTFE, modified PTFE, a composite material of different layer types or other suitable material that is preferably non-reactive with the process fluid. According to one embodiment, diaphragm 1002 can be approximately 0.013 inches thick. It should be noted that in other embodiments, separate diaphragms can be used for each valve and other types of diaphragms can be used.

FIG. 5A illustrates one embodiment of a side view of dispense block 205 having end surface 1000. FIG. 5B illustrates one embodiment of end surface 1000 of dispense block 205. For each valve, in the embodiment shown, end surface 1000 includes an annular ring into which an O-Ring partially pushes a portion of the diaphragm. For example, ring 1010 corresponds to input valve 125, ring 1012 corresponds to isolation valve 130, ring 1014 corresponds to barrier valve 135, ring 1016 corresponds to purge valve 130 and ring 1018 corresponds to vent valve 145. FIG. 5B also illustrates the input/output flow passages for each valve. Flow passage 1020 leads from the inlet 210 (shown in FIG. 3) to inlet valve 125 and flow passage 280 leads from inlet valve 125 to the feed chamber; for isolation valve 130, flow passage 305 leads from the feed chamber to isolation valve 130 and flow passage 1022 leads from isolation valve 130 to the filter; for barrier valve 135, flow passage 1024 leads from the filter to barrier valve 135 and flow passage 290 leads from barrier valve 135 to the dispense chamber; for purge valve 140, flow passage 300 leads from the dispense chamber and flow passage 305 leads to the feed chamber; and for vent valve 145, flow passage 1026 leads from the filter and flow passage 1027 leads out of the pump (e.g., out vent 215, shown in FIG. 3). Several of the above-referenced flow passages can be seen running through dispense block 205 in FIG. 3, above.

FIG. 6 is a diagrammatic representation of one embodiment of the outer side of valve plate 230. As shown in FIG. 6, valve plate 230 includes various holes (e.g., represented at 1028) through which screws can be inserted to attached valve plate 230 to dispense block 205. Additionally, shown in FIG. 6 are the valve control inlets for each valve to apply pressure or vacuum to the corresponding diaphragm. For example, inlet 235 corresponds to barrier valve 135, inlet 240 to purge valve 140, inlet 245 to isolation valve 130, inlet 250 to vent valve 145, and inlet 255 to inlet valve 125. By the selective application of pressure or vacuum to the inlets, the corresponding valves are opened and closed.

FIG. 7 is a diagrammatic representation of valve plate 230 showing the inner surface of valve plate 230 (i.e., the surface that faces dispense block 205). For each of inlet valve 125, isolation valve 130, barrier valve 135, purge valve 140 and vent valve 145, valve plate 230 at least partially defines a valve chamber into which a diaphragm (e.g., diaphragm 1002) is displaced when the valve opens. In the example of FIG. 7, chamber 1025 corresponds to inlet valve 125, chamber 1030 to isolation valve 130, chamber 1035 to barrier valve 135, chamber 1040 to purge valve 140 and chamber 1045 to vent valve 140. Each valve chamber preferably has an arced valve seat from the edge of the valve chamber to the center of the valve chamber towards which the diaphragm displaces. For example, if the edge of the valve chamber is circular (as shown in FIG. 7) and radius of the arced surface is constant, the valve chamber will have a semi-hemispherical shape.

A flow passage is defined for each valve for the application of a valve control gas/vacuum or other pressure to cause the diaphragm to be displaced between an open position and closed position for a valve. As an example, flow passage 1050 runs from an input on valve control plate 230 to the corresponding opening in the arced surface of purge valve chamber 1040. By selective application of vacuum or low pressure through flow passage 1050, diaphragm 1002 can be displaced into chamber 1040, thereby causing purge valve 140 to open. An annular ring around each valve chamber provides for sealing with O-rings 1004. For example, annular ring 1055 is used to partially contain an o-ring to seal purge valve 140. FIG. 8 is a diagrammatic representation of valve plate 230 made transparent to show the flow passages, including flow passage 1050, for the application of pressure or vacuum to each valve.

FIG. 9A is a diagrammatic representation of a valve plate design in which the displacement volume of the valve varies with the amount of pressure/vacuum applied to diaphragm 1002. Shown in FIG. 9A is an embodiment of a purge valve. In the example of FIG. 9A, a valve plate 1060 is connected to dispense block 205. Diaphragm 1002 is sandwiched between valve plate 1060 and dispense block 205. Valve plate 1060 forms a valve chamber 1062 into which diaphragm 1002 is displaced when vacuum is applied through flow passage 1065. An annular ring 1070 surrounding valve chamber seats o-ring 1004. When valve plate 1060 is attached to dispense block 205, o-ring 1004 presses diaphragm 1002 into annular ring 1016, which further seals the purge valve.

In the embodiment of FIG. 9A, valve chamber 1062 has chamfered sides to a substantially flat surface (indicated at 1067) towards which diaphragm 1002 displaces. When vacuum is applied to diaphragm 1002 through flow passage 1065, diaphragm 1002 displaces towards surface 1067 in a generally semi-hemispherical shape. This means that there will be some dead space (i.e., unused space) between diaphragm 1002 and valve plate 1060. This unused space is indicated at area 1070. As the amount of pull applied through flow passage 1065 increases (i.e., by increasing the vacuum), there is less unused space, however diaphragm 1002 does not completely bottom out. Consequently, depending on the pressure used to displace diaphragm 1002, the displacement volume of diaphragm 1002 changes (e.g., the amount of volume in the bowl of the fluid side of the diaphragm, generally indicated at 1072, changes).

When positive pressure is applied through flow passage 1065, diaphragm 1002 moves to seal the inlet and outlet (in this case flow passage 300 from the dispense chamber and flow passage 305 to the feed chamber). The volume of fluid in area 1072 will therefore be moved out of purge valve 140. This will cause a pressure spike in the dispense chamber (or other enclosed space to which the fluid is moved). The amount of fluid displaced by the valve will depend on how much volume was held up in the valve. Because this volume varies with the amount of pressure applied, different pumps of the same design, but operating using different vacuum pressures, will show different pressure spikes in the dispense chamber or other enclosed space. Moreover, because diaphragm 1002 is plastic, the displacement of diaphragm 1002 for a given vacuum pressure will vary depending on temperature. Consequently, the volume of unused area 1070 will change depending on temperature. Because the displacement volume of the valve of FIG. 11A varies based on the vacuum applied and temperature, it is difficult to accurately compensate for the volume displaced by the pump opening and closing.

Embodiments of the present invention reduce or eliminate the problems associated with a valve chamber having a flat surface. FIG. 9B is a diagrammatic representation of one embodiment of a purge valve using a valve plate design according to one embodiment of the present invention. Shown in FIG. 9B is an embodiment of purge valve 140. In the example of FIG. 9B, valve plate 230 is connected to dispense block 205. Diaphragm 1002 is sandwiched between valve plate 230 and dispense block 205. Valve plate 230 forms a valve chamber 1040 into which diaphragm 1002 can be displaced based on the application of vacuum (or low pressure) through flow passage 1050. An annular ring 1055 surrounding valve chamber 1040 seating o-ring 1004. When valve plate 230 is attached to dispense block 205, o-ring 1004 presses diaphragm 1002 into annular ring 1016, further sealing purge valve 140. This creates a seal and fixes diaphragm 1002. According to one embodiment, dispense block 205 can be PTFM, diaphragm 1002 PFTE or modified PTFE and valve plate 230 machined aluminum. Other suitable materials can be used.

In the embodiment of FIG. 9B, the area of valve chamber 1040 into which diaphragm 1002 displaces is semi-hemispherical. When vacuum is applied to diaphragm 1002 through flow passage 1050, diaphragm 1002 displaces towards the hemispherical surface in a semi-hemispherical shape. By sizing the semi-hemisphere of valve chamber 1040 appropriately, the hemisphere formed by diaphragm 1002 will match the shape of valve chamber 1040. As shown in FIG. 9B, this means that the dead space between the semi-hemisphere of diaphragm 1002 and the surface of the valve chamber (e.g., area 1070 in FIG. 9A) is eliminated. Moreover, because diaphragm 1002 displaces in a semi-hemispherical shape corresponding to the semi-hemispherical shape of valve chamber 1040, diaphragm 1002 will always have the same shape, and hence displacement volume, in its displaced position (this is illustrated in FIG. 10, discussed below). Consequently, the amount of hold up volume in valve 140 will be approximately the same regardless of the amount of vacuum applied (in the operational range of the valve) or temperature. Therefore, the volume of fluid displaced when purge valve 140 closes is the same. This allows a uniform volumetric correction to be implemented to correct for pressure spikes due to the displaced volume when the valve closes. As an additional advantage, the semi-hemispherical shaped valve chamber allows the valve chamber to be shallower. Moreover, because the diaphragm conforms to the shape of the valve seat, the stress on the diaphragm is reduced.

The valve chamber can be sized to allow the diaphragm to displace sufficiently to allow fluid flow from the inlet to the outlet path (e.g., from flow path 300 to flow path 305 of FIG. 3). Additionally, the valve chamber can be sized to minimize pressure drop while reducing displacement volume. For example, if the valve chamber is made too shallow, diaphragm 1002 may unduly constrict flow passage 305 for a particular application in the open position. However, as the depth of the valve chamber increases, it takes a stronger minimum vacuum to displace the diaphragm to its fully open position (i.e., the position in which the diaphragm is fully displaced into the valve chamber), leading to additional stress on the diaphragm. The valve chamber can be sized to balance the flow characteristics of the valve with the stress on the diaphragm.

It should also be noted that flow passage 1050 for the application of pressure/vacuum to the diaphragm does not have to be centered in the valve chamber, but may be off center (this is shown, for example, on the barrier valve chamber 1035 in FIG. 10). Additionally, the inlet and outlet flow passages to/from the valve can be positioned in any position that allows fluid to flow between them when the valve is open and to be restricted in the closed position. For example, the inlet and outlet flow passages to the valve can be positioned so that, when the valve closes, less of the fluid volume is displaced through a particular passage. In FIG. 9B, because the outlet flow passage 305 to the feed chamber is further from the center of the valve chamber (i.e., further from the center of the hemisphere) than inlet flow passage 300 from the dispense chamber, a smaller amount of fluid will be displaced through flow passage 305 than flow passage 300 when the valve is closed.

However, the positioning of these flow passages with respect to the valve can be reversed or otherwise changed in other embodiments so that less fluid is displaced back to the dispense chamber than displaced to the feed chamber when purge valve 140 closes. For inlet valve 125, on the other hand, the inlet flow passage can be closer to the center so that more fluid is displaced back to the fluid source than to the feed chamber when inlet valve 125 is closed (i.e., inlet valve 125 can have the inlet/outlet flow path arrangement shown in FIG. 9B). The inlets and outlets to various valves (e.g., barrier valve 135, outlet valve 147) can also be arranged, according to various embodiments of the present invention, to reduce the amount of fluid pushed into the dispense chamber when the valves close.

Other configurations of inlet and outlet flow passages can also be utilized. For example, both the inlet and outlet flow passage to a valve can be off center. As another example, the widths of the inlet and outlet flow passages can be different so that one flow passage is more restricted, again helping to cause more fluid to be displaced through one of the flow passages (e.g., the larger flow passage) when the valve closes.

FIG. 10 provides charts illustrating the displacement volume of various valve designs. Line 1080 is for valve design with a valve chamber having a flat valve chamber surface and a depth of 0.030 inches (e.g., the valve depicted in FIG. 9A), line 1082 is for a valve design having a semi-hemispherical valve chamber surface with a depth of 0.022 inches, line 1084 is for a valve design having a semi-hemispherical valve chamber surface with a depth of 0.015 inches (e.g., the valve depicted in FIG. 9B), line 1086 is for a valve having a semi-hemispherical valve chamber surface with a depth of 0.010 inches. The chart of FIG. 10 represents the amount of fluid volume displaced by the valve when the valve control pressure is switched from 35 psi pressure to vacuum. The x axis is the amount of vacuum applied in Hg (inches of mercury) and the y access is the volume displacement in mL. A minimum vacuum of 10 Hg is used to open the valves.

As can be seen from FIG. 10, the valve chamber with a flat valve chamber surface has a different displacement volume depending on the amount of vacuum applied (i.e., if 10 Hg is applied the displacement volume is approximately 0.042 mL, whereas if 20 Hg is applied the displacement volume is approximately 0.058 mL). The valves with hemispherical shaped valve chambers into which the diaphragm displaces, on the other hand, show an approximately constant displacement regardless of the vacuum applied. In this example, the 0.022 inch semi-hemisphere valve displaces 0.047 mL (represented by line 1082), the 0.015 inch semi-hemisphere valve displaces 0.40 mL (represented by line 1084) and the 0.010 inch semi-hemisphere valve displaces 0.30 mL (represented by line 1086). Thus, as can be seen in FIG. 10, a valve plate with semi-hemispherical valve chambers provides for repeatable displacement volumes as the vacuum pressure applied to the valve varies.

The valves of valve plate 230 may have different dimensions. For example, the purge valve 140 can be smaller than the other valves or the valves can be otherwise dimensioned. FIG. 11A provides an example of dimensions for one embodiment of purge valve 140, showing a hemispherical surface 1090 towards the diaphragm displaces. As shown in FIG. 11A, the valve chamber has a hemispherical surface with a spherical depth of 0.015 inches corresponding to a sphere with a radius of 0.3.630 inches. The edge of the semi-hemisphere is shown in Detail F. FIG. 11B provides an example of dimensions for one embodiment of input valve 125, isolation valve 130, barrier valve 135 and vent valve 145. In this embodiment, the spherical depth of the valve chamber is 0.022 inches corresponding to a sphere with a radius 2.453 inches.

The size of each valve can be selected to balance the desire to minimize the pressure drop across the valve (i.e., the desire to minimize the restriction caused by the valve in the open position) and the desire to minimize the amount of hold up volume of the valve. That is, the valves can be dimensioned to balance the desire for minimally restricted flow and to minimize pressure spikes when the valve opens/closes. In the examples of FIGS. 11A and 11B, purge valve 140 is the smallest valve to minimize the amount of holdup volume that returns to the dispense chamber when purge valve 140 closes. Additionally, the valves can be dimensioned to be fully opened when a threshold vacuum is applied. For example, purge valve 140 of FIG. 11A is dimensioned to be fully opened when 10 Hg of vacuum is applied. As the vacuum increases, purge valve 140 will not open any further.

FIG. 12 illustrates one embodiment of a diaphragm 1002. Diaphragm 1002, according to one embodiment of the present invention can be a single diaphragm used for each of input valve 125, isolation valve 130, barrier valve 135, purge valve 140 and vent valve 145. Diaphragm 1002 can be PTFE, modified PTFE or other suitable material that is preferably non-reactive with the process fluid. Example dimensions are shown in FIG. 12 and, according to one embodiment, diaphragm 1002 can be approximately 0.013 inches thick. It should be noted that in other embodiments, separate diaphragms can be used for each valve and diaphragms of other thicknesses can be used.

Although described in terms of a multi-stage pump, embodiments of the present invention can also be utilized in a single stage pump. FIG. 13 is a diagrammatic representation of one embodiment of a pump assembly for a pump 4000. Pump 4000 can be similar to one stage, say the dispense stage, of multi-stage pump 100 described above and can include a rolling diaphragm pump driven by a stepper, brushless DC or other motor. Pump 4000 can include a dispense block 4005 that defines various fluid flow paths through pump 4000 and at least partially defines a pump chamber. Dispense pump block 4005, according to one embodiment, can be a unitary block of PTFE, modified PTFE or other material. Because these materials do not react with or are minimally reactive with many process fluids, the use of these materials allows flow passages and the pump chamber to be machined directly into dispense block 4005 with a minimum of additional hardware. Dispense block 4005 consequently reduces the need for piping by providing an integrated fluid manifold. A pressure sensor can be positioned to read the pressure in the pump chamber.

Dispense block 4005 can include various external inlets and outlets including, for example, inlet 4010 through which the fluid is received, purge/vent outlet 4015 for purging/venting fluid, and dispense outlet 4020 through which fluid is dispensed during the dispense segment. Dispense block 4005, in the example of FIG. 13, includes the external purge outlet 4010 as the pump only has one chamber. U.S. Provisional Patent Application No. 60/741,667, entitled “O-RING-LESS LOW PROFILE FITTING AND ASSEMBLY THEREOF” by Iraj Gashgaee, filed Dec. 2, 2005, [Atty. Dkt. No. ENTG1760], and U.S. patent application Ser. No. ______, entitled “O-RING-LESS LOW PROFILE FITTINGS AND FITTING ASSEMBLIES”, by Inventor Iraj Gashgaee, filed _(——————) [Atty. Dkt. No. ENTG1760-1] which are hereby fully incorporated by reference herein, describes an embodiment of fittings that can be utilized to connect the external inlets and outlets of dispense block 4005 to fluid lines.

Dispense block 4005 routes fluid from the inlet to an inlet valve (e.g., at least partially defined by valve plate 4030), from the inlet valve to the pump chamber, from the pump chamber to a vent/purge valve and from the pump chamber to outlet 4020. A pump cover 4225 can protect a pump motor from damage, while piston housing 4027 can provide protection for a piston and, according to one embodiment of the present invention, be formed of polyethylene or other polymer. Valve plate 4030 provides a valve housing for a system of valves (e.g., an inlet valve, and a purge/vent valve) that can be configured to direct fluid flow to various components of pump 4000. Valve plate 4030 and the corresponding valves can be formed similarly to the manner described in conjunction with valve plate 230, discussed above. The purge valve can be the same size as, smaller than or larger than the inlet valve. Using a smaller purge valve, however, can reduce the holdup volume returned to the chamber as described above. According to one embodiment, each of the inlet valve and the purge/vent valve is at least partially integrated into valve plate 4030 and is a diaphragm valve that is either opened or closed depending on whether pressure or vacuum is applied to the corresponding diaphragm. In other embodiments, some of the valves may be external to dispense block 4005 or arranged in additional valve plates. According to one embodiment, a sheet of PTFE is sandwiched between valve plate 4030 and dispense block 4005 to form the diaphragms of the various valves. Valve plate 4030 includes a valve control inlet (not shown) for each valve to apply pressure or vacuum to the corresponding diaphragm.

Thus, embodiments of the present invention provide a valve design that reduces variations in displacement volume. According to various embodiments of the present invention, a valve body can define a valve chamber with a valve seat shaped to provide a fixed holdup volume. For example, the valve plate can have a semi-hemispherical shape to which the valve diaphragm conforms when a minimum vacuum is applied to the diaphragm. That is, the diaphragm substantially lines the inside of the semi-hemispherical surface when the valve is in the open position. It should be noted that the outer edge of the valve chamber does not have to be round, but can be elliptical or other shape. The surface of the valve chamber towards which the diaphragm displaces, however, is preferably shaped so that, when the diaphragm is displaced, the diaphragm takes the shape of that surface. Thus, the valve chamber can have a shape such that the diaphragm takes a known volume when the diaphragm is displaced (i.e., a shape that creates a fixed volume when the valve is open).

Although the present invention has been described in detail herein with reference to the illustrative embodiments, it should be understood that the description is by way of example only and is not to be construed in a limiting sense. For example, dimensions are not to be construed in a limiting sense. It is to be further understood, therefore, that numerous changes in the details of the embodiments of this invention and additional embodiments of this invention will be apparent to, and may be made by, persons of ordinary skill in the art having reference to this description. It is contemplated that all such changes and additional embodiments are within the scope of this invention. 

1. A valve comprising: a valve body defining: a valve chamber having a valve seat; an inlet flow passage; an outlet flow passage; a diaphragm control flow passage, wherein the diaphragm control flow passage intersects the valve seat; and a diaphragm movable towards and away from the valve seat, wherein the diaphragm control flow passage is separated from the inlet flow passage and the outlet flow passage by the diaphragm; and wherein the valve seat is shaped so that the valve has a fixed holdup volume when at least a threshold vacuum is applied to the diaphragm control flow passage.
 2. The valve of claim 1, wherein the valve seal conforms to the valve seat shape when at least the threshold vacuum is applied to the pressure control passage.
 3. The valve of claim 1, wherein the valve seat has a semi-hemispherical shape.
 4. The valve of claim 3, wherein the valve body comprises multiple pieces.
 5. The valve of claim 4, wherein a first portion of the valve body comprises a dispense block defining the inlet and outlet flow passages and a second portion of the valve body comprises a valve plate defining the valve seat and the diaphragm control flow passage.
 6. The valve of claim 6, wherein the diaphragm is sandwiched between the dispense block and the valve plate.
 7. The valve of claim 6, further comprising an o-ring at least partially disposed in a first annular ring defined in the valve plate, wherein the o-ring contacts the diaphragm.
 8. The valve of claim 7, wherein the dispense block comprises a second annular ring, wherein the diaphragm is partially disposed in the second annular ring.
 9. The valve of claim 5, wherein the inlet flow passage leads to a dispense chamber of a multi-stage pump.
 10. The valve of claim 9, wherein the inlet flow passage intersects the valve chamber at a center axis.
 11. The valve of claim 9, wherein the outlet flow passage intersects the valve chamber at a center axis.
 12. The valve of claim 9, wherein the inlet and outlet flow passage are both off-center.
 13. The valve of claim 9, wherein the inlet flow passage and outlet flow passage are different sizes.
 14. A valve assembly having a first valve, the valve assembly comprising: a valve body comprising a first piece coupled to a second a piece, wherein the first piece and the second piece define a first valve chamber, further wherein the first piece defines a first flow passage and a second flow passage intersecting the valve chamber and the second piece defines a first valve seat and a third flow passage intersecting the first valve seat; and a first valve diaphragm movable within the valve chamber, wherein the first and second flow passages are separated from the third flow passage by the first valve diaphragm; wherein the first valve seat is shaped so that the first valve diaphragm conforms to the first valve seat to provide a fixed first valve holdup volume when a threshold or greater vacuum is applied to the third flow passage.
 15. The valve assembly of claim 15, wherein the valve seat has a semi-hemispherical shape.
 16. The valve assembly of claim 14, further comprising a second valve having a second valve chamber.
 17. The valve assembly of claim 16, wherein the first portion of the valve body defines a fourth flow passage and a fifth flow passage, the fourth and fifth flow passages intersecting the second valve chamber; wherein the second portion of the valve body defines the second valve seat and defines a sixth flow passage intersecting the second valve seat; and wherein the second valve seat is shaped so that a second valve diaphragm conforms to the second valve seat to provide a fixed second valve holdup volume when a threshold or greater vacuum is applied to the sixth flow passage.
 18. The valve assembly of claim 17, wherein first valve seat and the second valve seat have semi-hemispherical shapes.
 19. The valve assembly of claim 17, further comprising an sheet of electrometric material coupled between the first portion of the valve body and the second portion of the valve body and wherein the first valve diaphragm is a first portion of the sheet of elastomeric material and the second valve diaphragm is a second portion of the sheet of elastomeric material.
 20. The valve assembly of claim 19, further comprising a first o-ring at least partially disposed in a first annular ring about the first valve seat and a second o-ring at least partially disposed about the second valve seat.
 21. The valve assembly of claim 17, wherein the first valve is a purge valve for a multistage pump.
 22. The valve assembly of claim of claim 21, wherein the second valve is one of an inlet valve, isolation valve, barrier valve or vent valve for a multistage pump.
 23. A multistage pump having a feed chamber and a dispense chamber, the multistage pump comprising: a pump body defining an inlet flow passage to and an outlet flow passage from a first valve; a valve plate coupled to the dispense body, the valve plate defining a first valve seat for the first valve; a first valve diaphragm movable in the first valve; and wherein the first valve seat is shaped so that the first valve diaphragm conforms to the first valve seat to provide a fixed first valve holdup volume when a threshold or greater vacuum is applied to the first valve.
 24. The multistage pump of claim 23, wherein the inlet flow passage to the first valve leads from the dispense chamber to the first valve.
 25. The multistage pump of claim 24, wherein an entrance to the inlet flow passage to the first valve is coaxial with a center axis of the first valve seat and an entrance to the outlet flow passage of the first valve is non-coaxial with the center axis of the first valve seat.
 26. The multistage pump of claim 24, wherein the entrance to the inlet flow passage to the first valve is non-coaxial with a center axis of the first valve seat and an entrance to the outlet flow passage of the first valve is coaxial with the center axis of the first valve seat.
 27. The multistage pump of claim 24, wherein the inlet flow passage to the first valve has a smaller cross-section than a cross-section of the outlet flow passage of the first pump.
 28. The multistage pump of claim 24, further comprising: an inlet valve diaphragm movable in an inlet valve; an isolation valve diaphragm movable in an isolation valve; a barrier valve diaphragm movable in a barrier valve; a vent valve diaphragm movable in a vent valve; and the pump body further defining a set of flow passages proving an inlet flow passage to and an outlet flow passage from each of an inlet valve, an isolation valve, a barrier valve and a vent valve; the valve plate further comprising, a valve seat for the inlet valve, a valve seat for the isolation valve, a valve seat for the barrier valve and a valve seat for the vent valve; and wherein the first valve is a purge valve.
 29. The multistage pump of claim 28, wherein the inlet valve seat is shaped so that the inlet valve diaphragm conforms to the shape of the inlet valve seat when the threshold or greater vacuum is applied to the inlet valve.
 30. The multistage pump of claim 29, wherein the inlet valve is larger than the purge valve.
 31. The multistage pump of claim 29, wherein: the vent valve seat is shaped so that the vent valve diaphragm conforms to the shape of the vent valve seat when the threshold or greater vacuum is applied to the vent valve; the barrier valve seat is shaped so that the barrier valve diaphragm conforms to the shape of the barrier valve seat when the threshold or greater vacuum is applied to the barrier valve; and the isolation valve seat is shaped so that the isolation valve diaphragm conforms to the shape of the isolation valve seat when the threshold or greater vacuum is applied to the isolation valve.
 32. The multistage pump of claim 31, wherein each of the first valve seat, vent valve seat, inlet valve seat, isolation valve seat and barrier valve seat have a semi-hemispherical shape.
 33. The multistage pump of claim 28, wherein the first valve diaphragm, vent valve diaphragm, barrier valve diaphragm, inlet valve diaphragm and isolation valve diaphragm are portions of a single sheet of elastomeric material coupled between the valve plate and the pump body.
 34. The multistage pump of claim 23, wherein the first flow passage leads from the dispense chamber to the first valve and the second flow passage leads from the first valve to the feed chamber. 